In a conventional circular knitting machine, the rotation of the needle cylinder and the concomitant movement and selection of the needles and yarn feed changeover mechanism are synchronously controlled to enable efficient knitting and to ensure high productivity. A sensor detects the rotational speed of the knitting machine and generates electrical signals having a strength proportional to the rotational speed of the knitting machine.
The generated electrical signals usually are transmitted based upon a predetermined trigger point corresponding to the time of sensing. For example, the sensor may sense cylinder speed at a select position of the needle cylinder and knitting needles. When the needle cylinder and needles are in this predetermined position the sensor senses the speed and generates a proportional electrical signal to the selection mechanism, which translates the electrical signals directly to mechanical movement of the mechanisms based upon the strength of the signal.
In older machines which operate at slower operating speeds, the electrical signal transmission based upon the timed trigger point did not adversely affect knitting machine efficiency. However, more modern machines are designed for high speed operation and include more yarn feeders for increased productivity. The conventional speed sensing and signal generating techniques are inadequate. The trigger point never changes whether the machine is slow or fast. At the moment when the cylinder and needle are in the predetermined position corresponding to the trigger point, the sensor generates the signal to the selection mechanism. During high speed operation of the knitting machine, the unmodified electrical transmission generates mechanical movement in the selection mechanism at the same speed whether the machine is slow or fast. As a result, during high speed knitting machine operation, the delay created by this process may cause the needle selection to become unstable. In extreme case, the errors in needle selection may cause a needle to break while impairing the texture of the knitted fabric.